Determining masses of supersymmetric particles

If supersymmetric particles are produced at the Large Hadron Collider it becomes very important not only to identify them, but also to determine their masses with the highest possible precision, since this may lead to an understanding of the SUSY-breaking mechanism and the physics at some higher scale. We here report on studies of how such mass measurements are obtained, and how the precision can be optimized.Comment: 11 pages, contribution to the proceedings "II. Southeastern European Workshop Challenges Beyond The Standard Model", 19-23 May 2005, Vrnjacka Banja, Serbi

Resolving ambiguities in mass determinations at future colliders

The measurements of kinematical endpoints, in cascade decays of supersymmetric particles, in principle allow for a determination of the masses of the unstable particles. However, in this procedure ambiguities often arise. We here illustrate how such ambiguities arise. They can be resolved by a precise determination of the LSP mass, provided by the Linear Collider.Comment: 6 pages, 6 figures, to appear in the proceedings of the 2005 International Linear Collider Workshop, Stanford, U.S.

Measurement of the Gluino Mass via Cascade Decays for SPS 1a

If R-parity conserving supersymmetry is realised with masses below the TeV scale, sparticles will be produced and decay in cascades at the LHC. In the case of a neutral LSP, which will not be detected, decay chains cannot be fully reconstructed, complicating the mass determination of the new particles. In this paper we extend the method of obtaining masses from kinematical endpoints to include a gluino at the head of a five-sparticle decay chain. This represents a non-trivial extension of the corresponding method for the squark decay chain. We calculate the endpoints of the new distributions and assess their applicability by examining the theoretical distributions for a variety of mass scenarios. The precision with which the gluino mass can be determined by this method is investigated for the mSUGRA point SPS 1a. Finally we estimate the improvement obtained from adding a Linear Collider measurement of the LSP mass.Comment: 40 pages; extended discussion of error

Mass Determination in Cascade Decays Using Shape Formulas

In SUSY scenarios with invisible LSP, sparticle masses can be determined from fits to the endpoints of invariant mass distributions. Here we discuss possible improvements by using the shapes of the distributions. Positive results are found for multiple-minima situations and for mass regions where the endpoints do not contain sufficient information to obtain the masses.Comment: to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 200

Mass ambiguities in cascade decays

We review the use of invariant mass distributions in cascade decays to measure the masses of New Physics (NP) particles in scenarios where the final NP cascade particle is invisible. We extend earlier work by exploring further the problem of multiple solutions for the masses.Comment: 4 pages, 4 figures, to appear in the proceedings of the XXXIII International Conference on High Energy Physics (ICHEP'06), July 26 - August 2 2006, Mosco

Russian Influence Operations on Social Media in Ukraine

Master i samfunnsvitenskap med fordypning i internasjonale relasjoner - 202

A User-centered system with blockchain in the Norwegian healthcare: From a security and privacy perspective

Master's thesis in Cyber security (IS507)With the current Covid-19 pandemic roaming the world, the IT attacks on the healthcare sector has increased five folds from 2019 to 2020. The Norwegian healthcare system is divided into different regions with their own systems respectfully. This fragmentation causes great communication issues between systems and exposes the transmitted data for attacks. To better combat this situation and improve upon the fragmented healthcare systems, a restructure is needed. In this thesis we explore the possibility of using blockchain technology as the foundation of a system that unifies the systems in the Norwegian healthcare sector. We adopt a Design Science Research approach to propose a blockchain-based architecture to solve the problem. Interviews with IT professionals in the Norwegian healthcare sector gave us their opinion about implementing blockchain and how the current systems are structured. Scalability was a common issue that different papers cited. There were multiple proposed solutions for this issue, but none seem practical for implementation today. It continues to be a difficulty and is one of the biggest reasons why we see hesitation in parts of the relevant sectors. Of course, blockchain has its upsides as well. Improved security and privacy with immutable ledgers make the system better suited for an increasingly exposed IT sector. It also provides a stronger availability since the same information is distributed between different nodes which take away the single failure point of regular database systems. The result from our evaluation of our proposed system is that it provides great user experience, increased security and privacy and better availability. Unfortunately, the benefits in these areas compared to the current systems are rather slim. Blockchain also introduces some performance penalty for smaller systems and scalability issues when the system becomes too large (with reference to storage and processing power). The conclusion is that a blockchain based healthcare system is better, but the amount of money and effort required to restructure the current system is too high and the demand for increased security is still too low. A more unified version of the current system could see good results, even without using blockchain

Invariant mass distributions in cascade decays

We derive analytical expressions for the shape of the invariant mass distributions of massless Standard Model endproducts in cascade decays involving massive New Physics (NP) particles, D -> Cc -> Bbc -> Aabc, where the final NP particle A in the cascade is unobserved and where two of the particles a, b, c may be indistinguishable. Knowledge of these expressions can improve the determination of NP parameters at the LHC. The shape formulas are composite, but contain nothing more complicated than logarithms of simple expressions. We study the effects of cuts, final state radiation and detector effects on the distributions through Monte Carlo simulations, using a supersymmetric model as an example. We also consider how one can deal with the width of NP particles and with combinatorics from the misidentification of final state particles. The possible mismeasurements of NP masses through `feet' in the distributions are discussed. Finally, we demonstrate how the effects of different spin configurations can be included in the distributions.Comment: 39 pages, 14 figures (colour), JHEP clas

Constrained invariant mass distributions in cascade decays. The shape of the "mqllm_{qll}-threshold" and similar distributions

Considering the cascade decay $D\to c C \to c b B \to c b a A$ in which $D,C,B,A$ are massive particles and $c,b,a$ are massless particles, we determine for the first time the shape of the distribution of the invariant mass of the three massless particles $m_{abc}$ for the sub-set of decays in which the invariant mass $m_{ab}$ of the last two particles in the chain is (optionally) constrained to lie inside an arbitrary interval, $m_{ab} \in [ m_{ab}^\text{cut min}, m_{ab}^\text{cut max}]$. An example of an experimentally important distribution of this kind is the ``$m_{qll}$ threshold'' -- which is the distribution of the combined invariant mass of the visible standard model particles radiated from the hypothesised decay of a squark to the lightest neutralino via successive two body decay,: \squark \to q \ntlinoTwo \to q l \slepton \to q l l \ntlinoOne , in which the experimenter requires additionally that $m_{ll}$ be greater than ${m_{ll}^{max}}/\sqrt{2}$. The location of the ``foot'' of this distribution is often used to constrain sparticle mass scales. The new results presented here permit the location of this foot to be better understood as the shape of the distribution is derived. The effects of varying the position of the $m_{ll}$ cut(s) may now be seen more easily.Comment: 12 pages, 3 figure

Supersymmetry and the LHC Inverse Problem

Given experimental evidence at the LHC for physics beyond the standard model, how can we determine the nature of the underlying theory? We initiate an approach to studying the "inverse map" from the space of LHC signatures to the parameter space of theoretical models within the context of low-energy supersymmetry, using 1808 LHC observables including essentially all those suggested in the literature and a 15 dimensional parametrization of the supersymmetric standard model. We show that the inverse map of a point in signature space consists of a number of isolated islands in parameter space, indicating the existence of "degeneracies"--qualitatively different models with the same LHC signatures. The degeneracies have simple physical characterizations, largely reflecting discrete ambiguities in electroweak-ino spectrum, accompanied by small adjustments for the remaining soft parameters. The number of degeneracies falls in the range 1<d<100, depending on whether or not sleptons are copiously produced in cascade decays. This number is large enough to represent a clear challenge but small enough to encourage looking for new observables that can further break the degeneracies and determine at the LHC most of the SUSY physics we care about. Degeneracies occur because signatures are not independent, and our approach allows testing of any new signature for its independence. Our methods can also be applied to any other theory of physics beyond the standard model, allowing one to study how model footprints differ in signature space and to test ways of distinguishing qualitatively different possibilities for new physics at the LHC.Comment: 55 pages, 30 figure